Poster sizes: what an A2 changes on the wall, in inches

Our sizes follow the A series, the paper standard used almost everywhere but North America: A4, A3, A2, A1, A0. They all share one shape, a rectangle 1.41 times taller than it is wide, which is why a piece composed in the editor prints at all five without losing an inch or being recropped. In inches: A4 is 8.3 × 11.7, A3 11.7 × 16.5, A2 16.5 × 23.4, A1 23.4 × 33.1, A0 33.1 × 46.8.

The series has a logic, and it helps you choose. Each size is the previous one folded in half: two A3 side by side make exactly one A2, two A2 make an A1. From one size to the next, each side grows by 41 % and the area doubles. The A0 is one square metre, by definition; the A4 is one sixteenth of it.

Landscape exists too, depending on the finish: for each size, the editor shows the finishes that take it, with the price.

It needs saying plainly, because it is the question everyone asks: a large print does not show more streets than a small one. The piece is a single file. What it draws, how much of the city, how many roads, how fine the buildings, is decided in the editor, by the framing and by the base map, clean or detailed. The size does one thing only: it enlarges that drawing, as it is.

What changes is the thickness of things. A street that is a hairline on an A4 becomes, on an A0, a line four times as wide. So does the title: a caption you read from three feet on an A4 reads from about six feet on an A2, and twelve on an A0. When choosing, look at the finest streets in your preview: what looks like a hair on screen will be a hair on an A4 and a firm line on an A1.

It is also why a star map likes room: its faintest points are looked at up close on an A4. On an A2, they hold the wall.

The sizes we list are those of the sheet and, for the classic frame, of the glazing. The moulding is 0.8 in wide: framed, the piece takes 1.6 in more in width and in height. A framed A2 covers 18.1 × 25 in of wall, a framed A0 34.6 × 48.4. It stands 0.9 in off the wall.

The framed canvas is a different object. The canvas is stretched on a 1.5 in deep bar, then set in a float frame that borders it at 0.2 in without touching it; the wood is 0.5 in wide. Count 1.3 in more each way, and above all 2.1 in of depth: it lives on the wall far more than a flat frame does, and that is what it is for. The edges of the bar are plain, black or white to match the paper of the piece: the drawing stays whole on the face.

The hangers, finally, hide nothing on the sides and take up to 0.6 in of the sheet at the top and at the bottom. The wooden bar is a little wider than the print: 12.6 in for an A3, 16.5 for an A2, 33.9 for an A0.

The rule decorators repeat fits in a fraction: above a piece of furniture, the print, or the group of prints, spans about two thirds of its width. Less, and it floats; more, and it crushes. The rest is arithmetic.

Orientation matters as much as size: turned sideways, a sheet takes the width of the next size up, at half the height. Above a 72 in sofa, you need around 48 in: a landscape A0 does it on its own, at 47 in. Upright, it is only 33: then a pair of A1 fills it. Above a 60 in queen bed, around 40: two framed A2 upright with a 4 in gap, or a landscape A1, wide and low. Above a 40 in console, an upright A1 or a landscape A2. On a shelf, an A4 or an A3, whichever way your design runs.

What the pair has going for it: a map and a sky, the place and the date, often read better as two than as one large piece. And at eye level: the centre of the piece at about 57 in, the convention galleries follow, and most people hang too high.